Rubber composition



Patented Nov. 3- 1931 UNITED STATES PATENT OFFICE ARCHIE R. KEMP, OF WESTWOOD, NEW JERSEY, ASSIGNOR T BELL TELEPHONE LABORATORIES, INCORPORATED, 033 NEW YORK, N. Y., A CORPORATION OF NEW YORK RUBBER COMPOSITION No Drawing. Originaliapplication filed August 24, 1927, Serial No. 215,235, and in Great Britain December 15, 1927. Divided and this application filed February 27, 1920. Serial No. 343,249.

In the specification of my application for U. S. Letters Patent, Serial No. 215,235, filed August 24:, 1927, there are described methods of treating rubber to render it electrically 5 stable under the continued influence of sea water and there is also described the product resulting from the use of such methods.

The present invention relates to compositions' of matter including as an essential constituent the rubber product resulting from treatment in accordance with the methods of the above mentioned specification or a similar product produced by equivalent methods.

; Insulating materials for under water cables 1 and more especially deep sea cables should possess suitable electrical characteristics, such as low dielectric constant and low dielectric losses stable and permanent under sea bottom conditions; properties rendering them easily extrusile such as a proper degree of thermoplasticity; suitable mechanical properties such as toughness, lack of brittleness, appropriate cold flow characteristics; and

. permanency under storage and sea bottom conditions; and for commercial utility, reasonable cost.

An object of the invention is to provide compositions of matter having the foregoing properties combined within a single substance.

A further object is to provide compositions of matter, primarily, for deep sea cable in sulation, and, secondarily, for other uses. and

we having properties as good or better for these purposes thangutta percha, which is relatively scarce and expensive.

Another object is to reduce the percentage of gutta percha employed in a submarine cable insulating composition.

A constituent of insulating material or other composition ofmatter in accordance with the invention is deproteinized rubber, under-which expression will be included rubher in which the proteins have been dispersed or have been'broken down and removed or have been otherwise modified to a sufiicient extent to render the rubber suitable for the intended purpose without, however, producing any-isomeric or polymeric'change in a substantial proportion of the rubber hydrocarbon molecules themselves.

A method of producing such a constituent is to immerse crude Hevea rubber in the form of crepe sheets in water in a pressure tank, then subject it to a temperature of 150 C. for 24 hours, wash for one hour in accordance with usual washing technique, and dry the rubber in a vacuum.

An alternative method is to dilute commercial Hevea latex containing ammonia as a preservative with live parts of water for each part of latex, heat the diluted mixture in a pressure tank at a temperature of 150 C. for 13 hours, cool to room temperature, coagulate with acetic acid, remove the coagulum and wash it for one hour at a temperature of C. and then air dry at room temperature.

The chemical, mechanical and electrical properties of products produced in accordance with the two foregoing methods are such as to render the products highly desirable as a constituent of compositions of matter, including other suitable ingredients, suitable for submarine cable insulation.

A second constituent is gutta percha or balata. For the purpose of this specification balata will be considered as a species of gutta percha. The gutta percha or balata may be deresinated before incorporation into the final product.

A third constituent comprises one or more lignite derivatives commonly known as Montan wax or Montan pitch. These lignite derivatives, when in commercial form, may be purified or refined before incorporation into the mixture.

Specification of the three principal constituents enumerated does not exclude from the product a proportion of ordinary rubber or of other waxes, thermoplastics, fillers, or preservatives, although in general such additional constituents are unnecessary and when included will ordinarily be in proportions relatively small as compared with the principal constituents. However, the invention includes compositions in which the second and third principal constituents are not both present as some desirable compositions may include only one of them.

A particular composition, prepared in accordance with the invention, consisted of 33% deproteinized rubber, prepared from crepe sheets, balata, and 37% Montan wax.

' Another composition comprised 29% deproteinized rubber, 36% balata, and Montan pitch.

The constituents of these compositions were milled. together and thoroughly commingled by methods well known in the art.

Another composition consisted of 20 pounds of deproteinized rubber, which was prepared from the crudeHevea rubber treated for 24 hours at 150 pounds steam pressure, washed one hour and dried in a vacuum, 20 pounds of commercial balata, 16 pounds of deresinated balata, and 35 pounds of Montan pitch. Samples of this composition in the form of sheets 0.05 in thickness were immersed in a 3.5% sodium chloride solution for four weeks at ordinary temperature and pressure, removed and dried in a uniform manner, placed between plane circular electrodes 5" in diameter and tested with an alternating current at a frequency of 1000 cycles per second at a temperature of 25 C. and atmospheric pressure. This test showed that the specimens had a dielectric constant of 2.5 and a phase difference angle of 21 min utes, 29 seconds, which corresponds to a value of the constant got 39.2, where G represents the conductance in micromhos per nautical mile and C represents the c apacitance in microfarads per nautical mile.

Another composition containing deproteinized rubber prepared from Hevea rubber sheet, 40% deresinated balata, and 20% Montan wax was similarly found to have a dielectric constant of 2.6 and aphase difference angle of 23'minutes, 37 seconds at ordinary temperature and' pressure, which cor- Another composition included 35% Hevea rubber sheet deproteinized in the form of latex, 30% deresinated balata, and 35% Montan wax refined by bleaching the powdered wax with cold benzine until the benzine was no longer highly colored. This compound had a dielectricv constant of 2.68 and a phase difference angle of 17 minutes at 25 C. at atmospheric pressure and 1000 cycles per secresponds to a value of of 43.2.

0nd, the corresponding value of g being 31.1.

I A cable core insulated with a composition containing equal parts of deproteinized rubher and deresinated balata had a dielectric constant of 2.6 and a phase difference angle of 9 minutes, 1 second, the corresponding value of being 16.5. The specific insu lating composition with which this cable core was insulated was firstinventedby Martell and is disclosed and claimed in his ap plication Serial No. 308,610, filed September 17, 1928.

The data given above relate to measurements taken at room temperature and at atmospheric pressure; the electrical properties of these materials do not change unfavorably when the compositions are subjected to the low temperature and high pressure existing at sea bottom. Thus a cable core insulated with the above mentioned compound containin 35% heat treated rubber 30% deresinate balata, and refined Montan wax having a length of 220 ft. and an outside diameter of 0.46" had an electrostatic capacity )er nautical mile of 0.313 microfarads an a con ductance of 17.2 micromhos per nautical mile at 25 0., atmospheric pressure and 900 cycles per second. When the pressure was increased to 5000 pounds per square inch and the temperature lowered to 0C. the capacity was found to be 0.316 microfarads and theconductance 12.2 micromhos. Itis interestingto note that gutta percha-insulated cable. cores do not change greatly in capacity withsuch. increased pressure and reduced temperature. asdescribed, but their conductance-increases under those circumstances about three times.

Thus, for example, a gutta percha insulated core of the above dimensions may be expected to have a conductance of about micromhos per nautical mile at deep sea pressure and temperature.

Tests, on the compositions described. and, other similar compositions have demonstrated that their physicaland chemical properties are satisfactory for submarine cable insulation.

In the following claims the word rubber willbe used to include various species of rubberand the word deproteinized will be used in conjunction therewith without discriminating between deproteinization of the The use of com sitions, such as described herein, is not limited to'submarine cable 111- sulation but they may be applied generally wherever compositions of similar characteristics are used.

What is claimed is:

1. A composition of matter suitable for insulating long submarine signaling cables, characterized in this, that the composition is composed chiefly of deproteinized rubber and gutta percha.

2. A composition in accordance with claim 1, characterized in this, that the gutta percha is deresinated before use.

3. A composition of matter in accordance with. claim 1, characterized in this, that the composition includes a substantial proportion of Montan lignite derivative.

4. A composition in accordance with claim 1, characterized in this, that the gutta percha includes a proportion of balata.

5. A composition in accordance with claim 1 including a substantial proportion of wax which is hard at room temperatures.

6. A composition of matter including de- )IOtGlDlZOCl rubber, gutta percha and Montan lignite derivative in substantially equal proportions.

'7. A composition of matter comprising det-roteinized rubber, balata and Montan lignite derivative.

8. A composition of matter comprising as principal constituents deproteinized rubber, deresinated balata and Montan Wax.

9. A composition of matter having as constituents between and 50% each of deproteinized rubber, balata and Montan lignite derivative.

10. A thermoplastic composition of matter, including a relatively large proportion of Hevea rubber hydrocarbon, substantially in its natural state of polymerization and having its natural nitrogenous content substanti ally reduced, and a Wax which is hard at ordinary temperature as a plasticizing agent, said composition being tough and non-brittle atordinary temperatures, capable of being extruded upon a signaling conductor, having cold flow characteristics similar to gutta percha, and which at sea bottom temperature and pressure has a dielectric constant around 3.0 or under and a phase diflerence angle of minutes or less when tested at a frequency of. 1000 cycles.

11. An insulating material suitable for insulating long submarine signaling cables and consisting of rubber hydrocarbon having its natural nitrogen content reduced more than and being intimately combined with gutta percha, and Montan lignite derivative.

12. An insulating material composed largely of rubber treated to have such stabilized electrical properties as are obtained by treating rubber in water for several hours under a steam pressure at a temperature considerably above 100 C'., thoroughly washing and drying, said treated rubber being and intimately intermingled with balata.

at around room temperature, atmospheric pressure and 1000 cycles than high grade gutta percha cable insulation.

16. A composition of matter in accordance with claim 1, in which the gutta percha c011- stituent consists of balata and is present in an amount substantially equal to the amount of deproteinized rubber.

In witness whereof, I hereunto subscribe my name this 23d day of February, 1929.

ARCHIE R. KEMP. 

